Có: \(\dfrac{a}{3}=\dfrac{b}{5}\)
\(=\dfrac{3a}{3.3}=\dfrac{b}{5}\)
\(=\dfrac{3a}{9}=\dfrac{b}{5}=\dfrac{3a+b}{9+5}=\dfrac{2}{14}=\dfrac{1}{7}\)
\(\Rightarrow\dfrac{a}{3}=\dfrac{1}{7}\Rightarrow a=\dfrac{\left(1.3\right)}{7}=\dfrac{3}{7}\)
Vậy số a thỏa mãn là \(\dfrac{3}{7}\)
Tick nha!!!